Case:
EMS brings in a 26-year-old male who reports he was stabbed in the back. He is speaking short phrases and complaining of a lot of pain on his right chest.
Primary Survey:
Airway intact, tachypnea with equal breath sounds bilaterally, strong pulses in all 4 extremities; GCS 15; small puncture wound superior to R scapula with no active bleeding
Vitals: HR 88, RR 24, BP 134/86, T 98.7F, SpO2 93% on RA
Secondary Survey:
No signs of head injury, no hemotympanum, no septal hematoma, no intraoral injuries
No midline spinal tenderness, full painless ROM of neck
Equal chest rise bilaterally, tachypnea, shallow breathing, cannot tolerate lying flat
Soft, nontender, nondistended
Small puncture wound superior to R scapula with no active bleeding or hematoma
Stable pelvis; normal rectal tone
Moving all extremities with no signs of injury; motor, sensation, and pulses intact
eFAST: no pericardial effusion; equal lung sliding in the apices and a small R sided pleural effusion; no intraperitoneal fluid
Upright CXR: no pneumothorax, good lung markings in all fields, sharp diaphragmatic angles b/l
A CT hours later demonstrates a large R sided pleural effusion that is concerning for hemothorax. When preparing for chest tube placement, you decide to use analgesic-dose ketamine in addition to intercostal blocks. However, the patient continues to scream in pain and you end up upgrading to dissociative-dose ketamine. Tube thoracostomy is completed and 800 cc blood is drained from the R hemithorax. After the ketamine wears off, the patient continues to complain of severe pain. He begs you, “Please doc, can you give me something more for the pain?” As you open the “Orders” tab, you wonder, Is there something else I can do for him? Is there a regional anesthetic nerve block that I can do?
Answer: yes! The SERRATUS ANTERIOR PLANE BLOCK
landmarks for serratus anterior plane block. source: Lin et al.(1)
Indication:
Anterior/lateral chest wall trauma (ie rib fractures, chest tubes)
Affected Area:
T2 to T9 dermatomes
Pros:
–Anticoagulation is not a contraindication
–Can be use on patients who cannot sit up for neuraxial blocks (ie erector spinae)
Cons:
–May not be effective for posterior chest wall trauma as block only covers lateral cutaneous branch of long thoracic nerve (see Figure 2)
Figure 2: Nerve anatomy of lateral chest wall. Source: ACEPNow (2)
Figure 3: vertical probe positioning. source: NYSORA (3)
Technique:
–Patient Position: supine, upright, or lateral recumbent; raise ipsilateral arm above head
–Probe Position: vertical or transverse in mid-axillary line at level of injury
–Needle Tip Position: between latissimus and serratus or between serratus and rib
–Anesthetic Amount: 30 cc of 0.25% bupivacaine (or anesthetic of choice)
injection sites: (left) between serratus and rib; (right) between latissimus and serratus. acronyms: ld = latissumus dorsi, sa = serratus anterior, r = rib. source: NYSORA (3)
Evidence:
Who would benefit from this block?
A case series (1) of 6 patients found that the serratus anterior plane block was effective as the sole analgesic for ED patients with rib fractures, herpes zoster, and requiring pigtail catheter placement.
Why would I want to do this block?
A retrospective, observational study (4) identified 34 patients admitted to a trauma service with 3+ rib fractures and found improved pain scores and incentive spirometry volumes after receiving serratus anterior plane block. This study was limited by its retrospective design.
Does it matter if I inject superficial or deep to the serratus muscle?
A case series (5) of 20 patients undergoing breast surgery found less opioid consumption post-operatively in patients who received a superficial block superior to the serratus muscle compared to a deeper block. This study was also significantly limited in its method and significantly prone to bias. Furthermore, while these results may suggest increased efficacy with a superficial approach, further investigation is required to determine if this would hold true for an ED population.
Theoretically, in patients with difficult-to-visualize anatomy, it may be safer to use a deep block with a rib as an landmark endpoint. (5) However, anatomically speaking it may be safer to go in the superficial plane in order to stay as far away as possible from the pleural line.
Potential Complications (and ways to avoid them):
–Inadequate anesthesia – hydrodissect with small amounts of saline/anesthetic to ensure you are in the correct plane before injecting the full amount
–Anesthetic-related toxicity if injected into vasculature – have lipid-emulsion available and stay within therapeutic range of anesthetic
–Pneumothorax if puncturing through pleura – always visualize needle tip and pleura with in-plane view; minimize risk with superficial approach
–Bleeding or hematoma development
–Infection – use sterile or semi-sterile technique
–Nerve damage – use blunt tipped needle
Summary/Take-Home Points:
–Consider serratus anterior plane block in patients with lateral/anterior chest trauma
—Serratus anterior plane block can be performed upright, supine, or lateral recumbent
–Anesthetic can be injected above or below the serratus anterior muscle
–Serratus anterior plane block can be used in isolation or as an adjunct to systemic pain medication
References:
Edited by: Robby Allen, PGY-3
lainey
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